1. Field of the Invention
The present invention concerns a new type of electrically conductive polymer film as well as a method for manufacturing it.
2. Description of the Prior Art
Conductive organic layers can be applied in many fields: electrostatic shielding, computer connections based on organic materials, shielding for S.H.F. applications, shielding for infrared applications etc. The techniques used to obtain these layers are common to the applications referred to, except for use in computer connections, where the layer must be pyrolyzed in order to obtain the required levels of conductivity.
The simplest technique used to obtain these layers consists in mixing a conductive powder (metal, carbon or electroactive polymer) in a macromolecular binder of the vinyl type (such as polyisoprene, polyvinyl chloride, etc.) or of the epoxy or polyurethane type. The electrical and dielectrical properties of the layers thus obtained depend not only on the properties of the matrix but also on the type of particles constituting the powder, their form (spherical or elongated) and the specific surface area of all the powder. However, regardless of the mixing protocol used to obtain conductive charged films, the material is only relatively homogeneous. This is because of the presence of microvacuums related to the existence of aggregates of conductive charges. This causes the material to be excessively charged beyond the percolation threshold and, hence, causes a reduction in the mechanical and filmogenic properties of films of this type. Furthermore, this method cannot used to manufacture a film with dielectrical and electrical properties which differ along the thickness and which would enable impedance matching.
According to another technique, conductive polymers are synthesized by electrolytic deposition through an expanded binder of reactive solvent covering one of the electrodes. This method gives interpenetrated films, but the random diffusion process cannot be supervised through the matrix (of polyvinyl alcohol or polyvinyl chloride) and does not enable these films to be homogeneous and highly charged.
In order to remove these drawbacks, the invention proposes a composite conductive polymer film consisting of a latex-based macromolecular matrix which is monodispersed in size, through which the electroplating of a conductive polymer is caused.